package observers

import (
	"github.com/mlange-42/arche/ecs"
	"github.com/mlange-42/arche/ecs/event"
	"github.com/mlange-42/arche/generic"
	"github.com/mlange-42/arche/listener"
)

// will be added as  an ecs.Resource to the world so we  can use it in
// CollisionSystem to dynamically make it appear or disappear
type EntityObserver struct {
	// we only have one obstacle so far, if we use multiple ones, turn
	// this in to a map, see player_observer.go for an example
	Entities map[ecs.Entity]int
}

func NewEntityObserver(world *ecs.World) {
	observer := &EntityObserver{}
	observer.Entities = make(map[ecs.Entity]int)

	resmanger := generic.NewResource[EntityObserver](world)
	resmanger.Add(observer)

	listen := listener.NewCallback(
		func(world *ecs.World, event ecs.EntityEvent) {
			observerID := ecs.ResourceID[EntityObserver](world)
			observer := world.Resources().Get(observerID).(*EntityObserver)
			observer.RemoveEntity(event.Entity)
		},

		event.EntityRemoved,
	)

	world.SetListener(&listen)
}

func GetEntityObserver(world *ecs.World) *EntityObserver {
	observerID := ecs.ResourceID[EntityObserver](world)
	observer := world.Resources().Get(observerID).(*EntityObserver)
	return observer
}

func (observer *EntityObserver) AddEntity(entity ecs.Entity) {
	observer.Entities[entity] = 1
}

func (observer *EntityObserver) RemoveEntity(entity ecs.Entity) {
	observer.Entities = make(map[ecs.Entity]int)
}